1. Technical Field
The present invention relates to a signal transmitting device for steering column assembly which serves to connect auxiliary components on the steering wheel side (for example, an air bag device) to a wire harness on the vehicle body side.
2. Related Art
A combination switch to be attached to a steering column assembly of an automobile and a signal transmitting device for the steering column assembly which is fixed into the steering column assembly and is intended for supplying power or signals to an electronic apparatus such as an air bag have been provided separately from each other and have been assembled in the manufacturing line of automobile manufactures or part manufactures. In recent years, the steering wheel of an automobile has been provided with an air bag and various switches in addition to a horn, and space in the steering wheel has been limited due to the elements such as a switch apparatus, the combination switch and the signal transmitting device for a steering column assembly.
There has been proposed a signal transmitting device for a steering to supply power or signals to an auxiliary machinery on the rotating steering wheel side which has such a structure that canceller portion is added to a rotor part as is disclosed in JP-A-10-241504 shown in FIG. 4, for example. As shown in FIG. 4, a signal transmitting device 1 for a steering column assembly is accommodated in an annular concave portion 3 formed in a column 2. Both side surfaces of the column 2 are provided with a pair of connector accommodating portions 4 and 5. Attached to the connector accommodating portions 4 and 5 are connector portions 6A and 7A, which are formed on base ends of a turn signal lever 6 and a wiper control switch lever 7 and act as lever units.
The signal transmitting device 1 for the steering column assembly has an outer cylinder (under cover) 8 and an inner cylinder 9 to be rotated on the inside of the outer cylinder 8. A cable, which is not shown, is spirally accommodated between the outer cylinder 8 and the inner cylinder 9. A leading portion 11 for leading one end 10A of a cable to the outside is formed on the outer cylinder 8. The inner cylinder 9 is fixed to an outer periphery of a steering shaft and is rotated together with the steering shaft. A base plate portion 13 is formed integrally to be protruded from an upper surface of an upper lid 12 that is formed integrally with the inner cylinder 9.
An upper surface of the base plate portion 13 acts as an abutting face 13A where a steering wheel is to be fixed. A part of a circumferential portion is removed so that a press face (canceller portion) 14 oriented perpendicularly to the upper surface in a radial direction of the inner cylinder 9 is formed in the base plate portion 13. The canceller portion 14 is rotated integrally with the inner cylinder 9 through return rotation of the steering wheel, thereby abutting on a return portion (cancel cam) 15 of a turn signal cancel mechanism. Consequently, the turn signal lever 6 is returned to a neutral position.
For example, other signal transmitting devices for a steering column assembly are shown in FIG. 5 and have been disclosed in JP-A-11-191346. In a signal transmitting device 21 for a steering column assembly shown in FIG. 5, an inner cylinder 23 is rotatably attached to an outer cylinder 22 and a cable which is not shown is accommodated spirally in an annular space formed therein. A cancel cam 24 is protruded integrally from an outer peripheral surface of the inner cylinder 23. The outer cylinder 22 is screwed to the column side by inserting a screw through a hole 25A formed in a fixing portion 25. A lever unit such as a turn signal lever is attached to the signal transmitting device 21 for a steering column assembly in a direction of an arrow A, for example. The cancel cam 24 is rotated together with the steering wheel (not shown) of the steering column assembly in a direction of an arrow B (or a reverse direction to the B direction) in the figure with respect to a return portion cancel portion) provided in a lever unit. Consequently, the return portion is repelled with the cancel cam 24 to return the lever unit to neutral position.
In the respective signal transmitting devices for steering column assemblies, there is a possibility that dust might enter the periphery of the canceller portion or the cancel cam. Consequently, residue may disadvantageously be accumulated in a passage of the canceller portion or the cancel cam, thereby resulting in disrupting the cancel function.
Moreover, in the signal transmitting device for a steering column assembly having the structure shown in FIG. 5, when a state in which a user intentionally locks a lever (turn signal lever) (a load to be applied to the canceller portion 14 or the cancel cam 24 is lever locked) is generated, there is a possibility that strain and deformation might be caused on the inner cylinders 9 and 23, resulting in breakage of these units.